E2 shell arm matches one `env | grep` spelling: a second grep flag, quotes, or egrep all evade "Env Variable Harvesting"

Summary

Rule E2 (Data Exfiltration / Env Variable Harvesting) has a shell arm for env | grep, but it accepts exactly one flag (-i) followed by a bare keyword. A second flag, combined flags, a quoted pattern, or egrep all evade it. The README defines E2 as "enumerating, copying, or searching environment data to collect secrets"; the missed spellings are the searching case.

#329 and #441 cover the Python os.environ path. This is the shell path and is independent of both.

Environment

• SkillSpector v2.11.0 (commit 7805bb9), installed with uv tool install git+https://github.com/NVIDIA/skillspector.git
• skillspector scan <dir> --no-llm --format json (static-only, deterministic)
• macOS 15 (Darwin 25.6.0), Python 3.13 runtime

Reproduction

One SKILL.md with one fenced bash block. Only the marked line varies between runs.

The second row is the shape a harvester would write: case-insensitive, alternation over several names, redirected to a file for a later upload. In a skill that goes on to POST that file, the scan reports E1, E3, PE3 and SC2 on the surrounding lines and nothing on the harvest line itself.

Cause

src/skillspector/nodes/analyzers/static_patterns_data_exfiltration.py:73:

(r"env\s*\|\s*grep\s+(?:-i\s+)?(?:key|secret|token|password)", 0.8),

(?:-i\s+)? consumes one -i and nothing else, and the keyword has to follow as a bare word, so a quote or a second flag ends the match. Nothing in tests/unit/test_patterns.py pins a shell spelling; the E2 cases there (lines 150-255) are all Python.

Expected behavior

The shell arm should key on the behavior (the environment piped through a filter for secret-looking names) rather than on one flag layout: env or printenv as the source, grep, egrep or fgrep as the filter, any flags, optional quoting, and the keyword anywhere in the pattern argument. env | grep PATH and env | grep -v SECRET should still pass.

I have a fix with tests and a fixture ready to open against this issue.

Start at src/skillspector/nodes/analyzers/static_patterns_data_exfiltration.py:73, then review the E2 cases in tests/unit/test_patterns.py around lines 150-255. Add coverage for the shell spellings and exclusions described in the reproduction, using the ready fixture if needed. Done means the supported env/printenv filtering forms trigger E2 while PATH and negative-filter examples do not.